There is known that the cerebrum activity of a subject can be measured by the chaotic analysis of the speech signal of the subject. Some exemplary processing devices are disclosed in JP-A-2001-348108 (patent reference #1), JP-A-2002-82734 (patent reference #2), JP-A-2001-116408 (patent reference #3), and JP-A-2001-280105 (patent reference #4).
The inventions disclosed in the patent references cited above attempt to obtain a biological signal of a subject including the speech signal to process the signal in accordance with a chaotic signal processing method in order to analyze and diagnose.
The devices and systems using the chaotic processing method as disclosed in the patent references cited above use any one of chaotic analysis well known in the art including such as Wolf's algorithm, Kantz' algorithm, Rosenstein's algorithm, Worel's algorithm, and Sano-Sawada's algorithm.    patent reference #1: JP-A-2001-348108    patent reference #2: JP-A-2002-82734    patent reference #3: JP-A-2001-116408    patent reference #4: JP-A-2001-280105